A fuel injection device has been used as a device for supplying fuel to an internal combustion engine. The fuel injection device includes an injector having a valve driven by a solenoid, a fuel pump that supplies fuel to the injector, and a regulator that controls pressure of the fuel supplied from the fuel pump to the injector to be kept constant. When such a fuel injection device is used to supply the fuel to the internal combustion engine, the device includes an injector drive circuit that applies a driving voltage from a battery to the solenoid of the injector and passes a driving current through the solenoid while receiving an injection command signal, and a control portion that receives a power supply voltage from the battery through a power supply circuit and is mainly constituted by a microprocessor, and the control portion provides the injection command signal to the injector drive circuit when fuel injection timing (timing for starting injection of the fuel) is detected. The injector opens a valve when receiving the injection command signal, and injects the fuel into an intake pipe or a cylinder of the internal combustion engine. Such a fuel injection device is disclosed in, for example, Japanese Patent Laid-Open No. 2002-21624.
An amount of fuel supplied from the injector to the engine (a fuel injection amount) is determined by pressure of the fuel supplied to the injector, and time for the injector opening the valve (fuel injection time). The pressure of the fuel supplied to the injector is kept substantially constant, and generally, the fuel injection amount is controlled by the fuel injection time. The injector does not start injection of the fuel immediately after the driving voltage is applied, but opens the valve and starts the injection of the fuel at a predetermined delay time after the driving voltage is supplied. Time between when the injector receives the driving voltage and when the injector starts the injection of the fuel is referred to as an ineffective injection time. The control portion regards actual injection time plus the ineffective injection time as apparent injection time, and supplies an injection command signal having a signal width equal to the apparent injection time is provided to the injector drive circuit. As disclosed in Japanese Patent Laid-Open No. 2002-21624, the ineffective injection time of the injector varies depending on the driving voltages supplied to the injector. Generally, the ineffective injection time is reduced with increase in the driving voltage supplied to the injector. If the driving voltage is reduced in the opening process of the valve of the injector to increase the ineffective injection time, the actual injection time is reduced to cause a shortage of fuel injection amount. Thus, in order to precisely inject a predetermined amount of fuel, it is necessary to prevent a reduction in the driving voltage in driving the injector.
Generally, an electrical component other than the injector drive circuit and the control portion as a further load is connected to a battery. When the internal combustion engine is a gasoline engine and uses an ignition device using a battery as power supply, the further component includes an ignition device for an internal combustion engine.
A known ignition device for an internal combustion engine using a battery as power supply is a capacitor discharge ignition device including a DC converter that increases a voltage of the battery, and a capacitor discharge ignition circuit that uses the DC converter as a capacitor charging power supply. As disclosed in Japanese Patent Laid-Open No. 9-209893, the capacitor discharge ignition circuit is comprised of an ignition coil, a capacitor provided on a primary side of the ignition coil and charged to one polarity by an output of the DC converter, and a discharge switch that turns on when receiving an ignition signal and discharges charges accumulated in the capacitor through a primary coil of the ignition coil.
When such an ignition device is used, means for controlling ignition timing is further provided in the control portion. In this case, the control portion arithmetically operates ignition timing of the internal combustion engine for various control conditions, and provides an ignition signal to the discharge switch when the arithmetically operated ignition timing is detected. When the ignition signal is provided to the discharge switch, the discharge switch turns on and thus discharges the charges in the capacitor through the ignition coil, and the discharge induces a high voltage for ignition in a secondary coil of the ignition coil. The high voltage is applied to an ignition plug mounted to a cylinder of the engine, and thus spark discharge occurs in the ignition plug to ignite the engine.
As an ignition device using a battery as power supply, a current interruption ignition device is also known that interrupts a current having passed from a battery through a primary coil of an ignition coil when ignition timing is detected to induce a high voltage for ignition in a secondary coil of an ignition coil, but detailed descriptions thereof will be omitted. As the electrical component other than the injector drive circuit and the control portion, an electric actuator for operating a throttle valve of the engine or an exhaust valve may be provided.
As described above, in the case where the further electrical component as the load is connected to the battery to which the injector drive circuit and the control portion as the loads are connected, the driving voltage of the battery may be significantly reduced if the ignition command signal is generated with electric power being consumed by the further load and the driving current passes from the battery through the solenoid of the injector. If the driving voltage applied from the battery to the injector is significantly reduced, the ineffective injection time may be increased to cause a shortage of actual injection time and a shortage of fuel injection amount.
Thus, in the control device disclosed in Japanese Patent Laid-Open No. 2002-21624, the fuel injection device and the further load are not simultaneously driven. In the control device, the current interruption ignition device is used as the ignition device for igniting the engine, and driving of at least one of the injector and the fuel pump is stopped while the primary current passes through the ignition coil of the ignition device.
The construction as disclosed in Japanese Patent Laid-Open No. 2002-21624 can prevent a reduction in the battery voltage and an increase in the ineffective injection time in the process of opening the valve of the injector. However, if the injector is not driven while the current passes from the battery through the ignition device, and a period in which a large current passes from the battery through the ignition device matches a period in which the injector is driven, fuel injection to be performed is not performed, thereby causing another problem of a shortage of amount of fuel supplied to the engine. There is no problem if the period in which the large current passes from the battery through the ignition device does not match the period in which the injector is driven, but it is difficult that the period in which the current passes through the ignition device does not match the period in which the injector is driven both during low speed rotation and high speed rotation.
In the invention disclosed in Japanese Patent Laid-Open No. 2002-21624, if the driving of the fuel pump is stopped when the current passes from the battery through the ignition device, the injector can be driven. In this case, however, the injector is driven with the current passing from the battery through the ignition device, and thus the problem cannot be solved that the battery voltage is reduced in the process of opening the valve of the injector to cause the shortage of fuel injection amount.